You can volt mod it so it runs at 7v with a bit of rewiring. If it's plugged into your mobo (unlikely) you can use software, like Speedfan. If you want to be able to adjust it you could get a rheobus or fanbus for all of your fans or a single device rheostat like a
Zalman Fan Mate You might need a 4 to 3 pin connector for that though. Oh, and check and see if you have any "Fan Only" molexes on your PSU. I do on my Antec.
Luck!